This invention relates to multi-barrel carburetors and, more particularly, to a carburetor improvement for improving vacuum staging of the carburetor.
U.S. Pat. No. 3,940,459 discloses a four-barrel carburetor having a push rod on which is carried a metering rod carrier arm. A fuel metering rod is attached to each end of the arm. The lower end of the push rod is contacted by a cam follower which is raised and lowered in response to rotation of a cam carried on a throttle shaft of the carburetor. The upper end of the push rod is threaded and a vacuum step-up piston is carried on the upper end of the rod. A spring bears against the lower end of the piston and pushes the piston upward when engine vacuum decreases. During qualification of carburetors of this type, the position of the piston on the push rod is adjusted to meet the carburetor fuel flow curve. Because the degree of adjustment between carburetors may vary, the tension created on the spring will vary from one carburetor to another. As a consequence, the vacuum step-up response of one carburetor during part-throttle operations may differ markedly from that of another similar carburetor.